The total expected number of patients to be randomized is 72. Taking into account a relevant difference of 1.5 between groups on the NRS, with an SD of 2, 30 patients per group (60 patients in total) will be required to detect a statistically significant difference with a power of 80% at an alpha of 5% (two-tailed) for unpaired Student's T test. Taking into account a 20% drop out rate, 72 patients are expected to be randomized for this study.